Motor control system



June 1937. F. B. POWERS MOTOR CONTROL SYSTEM Filed Aug. 29, 1936 Patented `lune 1, 1937 MOTOR CONTROL SYSTEM Frank B. Powers,

Westinghouse Electr-i Dany, East Pittsburgh,

Pennsylvania Application August 29 8 Claims.

My invention relates, generally, to motor controlsystems, and more particularly, to systems for controlling the acceleration and the deceleration of electrically propelled vehicles.

An object of my invention, generally stated, is to provide a system for automatically controlling both the acceleration and the deceleration of an electrically propelled vehicle which shall be simple and efficient in operation, and which may be economically manufactured and installed.

A more specific object of my invention is to provide for maintaining predetermined rates of acceleration and deceleration of a vehicle regardless of the load on the vehicle.

Another object of my invention is to provide for regulating the motor current during both the acceleration and the deceleration of a vehicle in accordance with the load ron the vehicle.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

According to the preferred embodiment of my invention, both the acceleration and the deceleration of the propelling motors of an electric vehicle are controlled by an accelerator of the type described in Patent No. 1,991,229, issued February 12, 1935, to L. G. Riley and assigned to the Westinghouse Electric & Manufacturing Company. The accelerator is driven by a pilot motor under the control of a current limit relay which is responsive to the main motor current. Substantially constant rates of acceleration and deceleration are maintained regardless of load conditions by adjusting the setting of the limit relay in accordance with the load by means of a variable-load mechanism interposed between the car body and one of the vehicle trucks. The mechanism comprises a movable arm which is so connected to a variable shunt in the motor circuit that the current in the coil of the limit relay is varied in accordance with the distance between the car body and the truck, and, therefore, in accordance with the load on the vehicle.

For a fuller understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure l is a diagrammatic view of a control system embodying the invention, and

Fig. 2 is a chart, showing the sequence of operation of a portion of the apparatus illus` 55 trated in Fig. 1.

Wilkinsburg, Pa., assignor to c & Manufacturing Com- Pa.., a corporation of 1936, Serial No. 98,438

Referring to the drawing, electric motors Ill and II may be utilized for propelling a vehicle only a portion of which is shown. The motor I is provided with an yarmature winding I2, a series field winding I3, and a separately ex- 5 cited field winding I4. Likewise, the motor II is provided with an armature winding I5, a series field winding I6 and a separately excited field winding I1. The eld windings I4 and I1 are utilized during dynamic braking to assure 10 that braking action will take effect quickly.

An electrically operated line switch LS is provided for connecting the motors Il! and II to a trolley I8, which engages a power conductor I9 that may be energized from any suitable source of power such as a generating station (not shown). Energization of the separately excited eld windings I4 and I1 is controlled by switch T, which is closed to connect these field windings to the trolley I8 during coasting vand 20 dynamic braking of the vehicle.

Both the acceleration and the deceleration of the motors I0 and Il is primarily controlled by a motor driven accelerator A, which is of the same general type as the one described in the aforementioned Patent No. 1,991,229. The accelerator A comprises a circular copper bus 20 inside of which are disposed a plurality of ccntact fingers 2l to 42, inclusive, which are progressively forced against the bus 20 by a revolv- 30 ing roller '43.

The roller 43 is driven by a pilot motor 44 through shafts 45 and 46 connected by beveled gears 41. The pilot motor 44 is provided with an armature winding 48 and two field windings 35 49 and 50, one for each direction of rotation.

A spring actuated brake 5I is provided for stopping the motor 44, a brake release coil 52 being connected in series with the armature Winding 48 of the pilot motor and is, therefore, deener- 40 gized when the motor is deenergized.

The accelerator A is provided with a resistor 53 that is divided into a number of sub-divisions which are connected to the Contact fingers 2| to 42, inclusive. A major portion of the re- 45 sistor 53 is connected in the armature circuits of the motors I0 and II and is utilized to control the armature current during acceleration of the vehicle. 'I'he entire resistor 53 may be utilized to control the current ilowing in the motor circuit during dynamic braking.

As shown, a number of cam switches AI, A2, A3, A4, B, C, D, E and F are located in the accelerator and are actuated by the shaft 46. The reference numerals 2l to 42', inclusive, 55

indicate the contact lingers over which the roller 49 travels while the cam switches are closed. The function of the various cam switches will be explained more fully hereinafter.

5 In addition to the accelerator and the cam switches, several other switches are provided for performing certain switching operations. 'Ihese switches include a switch M i for connecting the motors I9 and Il to the resistor 53 during accel- 10 eration, a switch M2 for connecting one terminal of the motors directly to ground after a maior portion of the resistor 99 has been shunted from the motor circuit by the accelerator roller 99, and switches BI and B2 for establishing dynamic 16 braking connections for the motors I9 and il.

Drum controllers MC and BC are provided for controlling the motor connections during acceleration and braking, respectively. 'Ihe controllers are electrically interlocked in the usual manner to prevent improper operation of the equipment.

In order to prevent a sudden rush of current upon the ref-application oi' power or dynamic braking after coasting of the vehicle, a spotting relay SR is provided to change the position of the 26 accelerator roller during coasting to approximately match the car speed. The shunt field windings i9 and I1 of the motors III and il, respectively, are energized during coasting by the closing oi' the switch T to connect the shunt eld windings to the power conductor I9. Therefore the motors develop a voltage which is proportional toV the speed of the car.

Since the actuating coil l! oi' the relay SR is connected across the amature ci.' the motor I i. the relay is responsive to the speed of the car. As the speed decreases, the contact members of the relay are closed, thereby lcausing the pilot motor 44 to return the accelerator roller toward the nrst contact finger. The backwardfmovement of the accelerator operates one of the cam switches AI, A2, A9 or A9 to cut a portion of a resistor I9 out of the relay coil circuit. The contact members oi the relay are then opened, holding the accelerator until the car speed has been further reduced, when the accelerator is again moved backward by the closing of the relay contacts. This operation is repeated until the master controller is moved out ofthe coasting position, or until the accelerator is returned to the ilrst position.

A current limit relay L functions to control the motor current both during acceleration and dynamic braking by regulating the operation of the accelerator A. The contact members of the limit relay are disposed to shunt the armature of the pilot motor u when closed, thereby stopping the accelerator.

With a view toward maintaining a substantially constant rate of :acceleration regardless of load conditions on the vehicle, I provide a means for adjusting the setting of the limit relay L in accordance with the load on the ,vehicle As shown, the actuating coil ot the limit relay L is connected across a variable shunt 91 by means of a movable arm 59 disposed to engage the shunt l1. Since the shunt 91 is connected in the motor circuit, the limit relay L is responsive to the motor current and the proportionate amount oi' cur- -rent passing through the coil of the limit relay may be varied by changing the position oi' the movable arm 99 on the shunt 91.

As shown, the movable arm I9 is pivotally mounted upon the frame structure I9 of the vehicle which is reslliently supported by a vehicle truck 99, which may be of any suitable oonstl'lltaosaoas tion. The arm I9 is so connected to a suitable linkage mechanism 9| that it is moved across the shunt 51 in accordance with the load carried by the vehicle. One end of the link 9| is connected to one end of a pivotally mounted bar i2, carried by a bracket 99 which is secured to the frame 59. The other end of the bar 62 is disposed to engage an inclined surface of a movable member 69 disposed between suitable guides on the bracket 99. The bottom of the member il rests upon a portion of the vehicle truck 99 which is not deflected by changes in the load carried by the truck. Thus, it will be seen that as the load on the vehicle is increased to depress the springs of the truck iii, the member 6l is pushed upwardly to actuate the arm 82 which, in turn, moves the arm 59 across the shunt 51. As the load decreases, allowing the springs of the truck to raise the frame I9 and the bracket 93, a spring il actuates the arm 58 in the opposite direction. 4

In order that the functioning oi' the foregoing apparatus may be more clearly understood, the operation of the system will now be described in more detail. Assuming that a control switch 99 has been closed, the motors I 9 and Il may be connected to the power source to start the vehicle by actuating the master controller MC to position a to close the switches LS and Mi. The energizing circuit for the actuating coil of the switch LS may be traced from a power conductor 91, which is connected to the trolley i9 through the control switch 96, conductor 69, contact iingers 99 and 1i bridged by a contact segment 12 on the master controller MC, conductor 19, an interlock 19 on the switch B2, conductors 1I and 19, the actuating coil 11 of the switch LS and conductor 19 to the grounded conductor 19. 'Ihe energizing circuit for the actuating coil ior the switch MI extends from the previouslyenergized conductor 16 through the actuating coil 9| of the switch MI and the conductor 19 to the grounded conductor 19. f

'I'he closing of the switches-LS and Mi connects the motors I9 and I i to the power source in parallel circuit relation and in sexies with a major portion of the resistor 5I in the accelerator A. 'Ihe circuit through the motor I Il may be traced from the power conductor 91 through contact members Il of the switch LS, conductors 94 and 9|, the armature winding I2 and series field winding I9 oi' the motor il, conductor 99. contact members 9-1 of the switch Ml, conductor 99, the resistor I9, contact linger 2| which is compressed against the bus 20 by the roller 92 and conductor 99 to the grounded conductor 19. 'I'he circuit through the motor II extends from the conductor 99 through the series neld winding i9 and armature winding Il, a conductor 9i, the shunt l1, and the conductor 88 to the contact members 91 of the switch Mi and thence through the circuit previously traced to the grounded conductor 19. Since a major portion oi the resistor 59 is connected in series with the motors, the vehicle will be operated at a slow rate of speed.

If it is desired to accelerate the vehicle, the master controller MC may be actuated to position b thereby energizing the pilot motor 44, which operates the roller 43 to cut the resistor Il out of the motorcircuit, the operation of the motor Il being under the control of the limit relay'. L, as will be explained more fully hereinafter, The energizing circuit for the pilot motor M may be traced from a contact finger 92 which engages the contact segment 12 oi' the controller MC through conductor 93, cam switch B of the accelerator A, conductor 84, the eld winding 48 of the pilot motor 44, the armature winding 48, conductor 95, the release coil 52 of the brake 5| and conductor 98 to the grounded conductor 19. As explained hereinbefore, the energization of the coil 52 releases the brake 5| which permits the motor 44 to operate the accelerator A.

The rotation oi the roller 43 compresses the contact iingers on the accelerator against the l0 bus 2l to shunt the resistor 53 from the motor circuit. The shunting of a portion of the resistor 53 will permit the motor current to increase to a value which will operate the limit relay L tov establish ya shunt circuit around the amature of the motor 44 and the brake release coil 52, thereby stopping the accelerator. This shunt circuit may be traced from one terminal of the armature 48 through conductor 91, contact'mem-V ber 98 on the limit relay L and conductor 89 to the grounded conductor 18. When the .main motors have accelerated to a speed which will cause the motor current to be reduced to a value that will permit the relay L to open its contact members, the pilot motor 44 advancesthe vac'l load mechanism associated with the truck in causes the arm 58 to be moved toward the righi;`

on the shunt 51, thereby decreasing the proportionate amount of motor current which passes through the actuating coil oi the limit relay L.

In this manner, the motors III andy are supplied with a higher value of current before the limit relay L operates to stop the progression of the accelerator A, thereby maintaining the accelerating rate of the vehicle at a substantially constant rate regardless of the load on the vehicle, within the limits of the capacity of the motors ||I and lShould the load on the vehicle be decreased below a predetermined amount, the arm 58 is moved towards the letton the shunt 51 which increases the energizing, current for the limit relay L, thereby decreasing=` the amount of current supplied to the motors III and and preventing the vehicle from being setting oi' the limit relay L in accordance vwith the load carried by the vehicle.

This operation is continued until the accelerator roller 43 reaches the contact finger 33, at which time the cam switch D is closed to energize the actuating coil of the switch M2. The energizing circuit for the coil of the switch M2 may be traced from the previously energized conductor 1B through the actuating coil ||I|, conductor |02, the cam switch D and conductor `|88 to the grounded conductor 18. The/closing of the switch M2 connects the motors I0 and II di'- Y rectly to ground through a circuit which extends from the conductor 86 through conductor |04, contact members |85 and conductor |06 to the grounded conductor 18, thereby causing maximum voltage to be applied to the motors.

However, the pilot motor `44 will continue to advance the roller 43 to the contact ringer 42 in order that the full amount of thev resistor 53 will be available for controlling the motor conductor during dynamic braking of the motors. The advancement oi the roller 43 is stopped by accelerated above its normal rate because of the decrease in load. Thus, it will be .seen that the variable load feature automatically adjusts the the opening oi the cam switch B to deenergize the pilot motor 44.

Assuming that it is desired to permit the vehicle to coast, the master controller MC may be actuated to the otr position, thereby opening the switches LS, MI and M2 to disconnect the motors and I| from the power source. At this time, the switch T is closed to connect the iield windings I4 and I1 to the power source, thereby separately exciting these windings and causing them'o'tors and to generate a voltage proportional to the speed of the. vehicle. The energizing circuit for the actuating coil oi' the switch T may be traced from the contact iinger |01, which engages the contact segment 12, conductor |08, the actuating coil |8801' the switch T, conductor III, the cam switch F and conductor v||I3 to the grounded conductor 18.v 'I'he circuit through the held' windings" |4 and I1, established by the closing of the switch T, may be traced from the power conductor 81 through conductor ||2, contact members ||3 oi' the'switch T, conductor ||4, the vfield windings I1, a resistor IIS,

the field winding' I4 and conductor I Il to the vgrounded conductor 18.

As describedj-hereinbefore the relay SR, which is connected yacross the armature oi the motor II,

functions, to"'m atch the position ofthe roller 43 `0n the accelerator lA with the speed of the vehicle, in orde'rthat the proper amount of the resistor 53 willbe available for controlling the motor current infthe event that dynamic braking yis establishedflhe energizing circuit for the 'actuating coil of therelay SR may be traced from one terminal `of'th'c armature winding I! of the motor II through a conductor |I1, the actuating coil 55 of the relay8R.conductor ||8, an interlock Il! on the switch M|,conductor |2I, an Vinterlock |22 on the switch BI, conductor |23, the resistor I6 and' conductors |24 and 8| to the other terminal of. the armature winding Ii.

When the vehicleisy Acoasting at a relatively high speed, energizatiofeoi'.- the ,relay SR causes itsv contact membersto be opened and the accelerator roller 43,.,rel'iiaiialbn thev last contact nnger.

42. As thfejspeediod the vehicle decreases, the

voltage produced byQ-the motor II will l l and the v contact. members of the rientri-:8B are permitted toclose; thereby causing the pilot'motor 44 to operate -ftlie accelerator roller 43 in a counter-clockwise direction: The energizing circuit ior the pilot motor 44 may be traced from a contact nnger |25` on the master controller HC through conductor |25, contact Vnngers |21 and |28 bridgedby a segment |28 on the braking controller BC, conductor |3|, an interlock |32 ou the switch T, conductor |38, contact members |34 on the relay SR; conductorsk |35 and |38, contact iingers |31 and Dlllbridged by segment |38 on the controller MC, conductor |4I, the cam switch C on the accelerator A; conductor |42, the neld winding 88 andthe amature winding 48 of the pilot motor l44, conductor u, the brake coil 52 and conductor tojjthe grounded conductor 13.

As previously explained.. the backward movement of the acceleratorA causes the cam switch A4 to cut4 a portionof Il out of the circuit for the actuatinlg coil-ofthe spotting relay SR thereby causing thecontact members of the relay to be opened to stop the accelerator until the speed of the vehicle has decreased still further, when the foregoing operation is repeated. In this manner, the spotting relay SR and the cam switches AI to' A4, inclusive, cooperate to match the position of the accelerator roller with the speed of the vehicle, thereby ensuring that the proper amount of resistance 53 will be available to control the motor current in the event that dynamic braking is established or power is 5 applied to the motors l0 and by reconnecting them to the power source.

If it is desired to decelerate the vehicle by means of dynamic braking, the braking controller BC may be actuated to position I to close the switches BI and B2 to establish dynamic breking connections, provided the controller MC is in the 01T position. The energizing circuit for the actuating coil of the switch BI may be traced from a contact finger |43 which engages the contact segment |29 through conductor |44 an interlock |45 on the switch LS, conductor |46, the actuating coll |41 of the switch BI, conductor |48, the cam switch E and conductor |03 to the grounded conductor 19. A holding circuit for the coil |41 is established through an interlock |49 by the closing of the switch BI. The holding circuit may be traced from the conductor |48 through the interlock |45 and the conductor 18 to the grounded conductor 19. The energizing 26 circuit for the actuating coil of the switch B2 extends from the previously energized conductor |46 through the actuating coil |5| of the switch B2 and the conductor 18 to the grounded conductor 19.

The closing of the switches Bl and B2 establishes dynamic braking connections for the motors and whereby the series field winding of one motor is connected across the armature winding of the other motor in a manner to cause the motors to function as generators to retard the movement of the vehicle. The circuit for the motor I0 may be traced from one terminal of the armature winding |2 through conductor 85, the field winding I6 of the motor conductor ||1, contact members |52 of the switch B2, conductor |53, the resistor 53, the contact nger 42, assuming that the accelerator roller 43 is on the finger 42, the bus 20, conductors 89 and 19, contact members |54 of the switch BI and conductor i5 |55 to the other terminal of the armature winding I2. The circuit for the motor Il may be traced from one terminal of the armature winding |5 from the conductor |1, the contact members |52 of the switch B2, conductor |53, the resistor 53, contact finger 42, the bus 20, conductors 89 and 19, contact members |54 of the switch BI, conductor |55, the field winding I3, conductor B5, the shunt 51 and conductor 9| to the other terminal of the armature winding I5. 55 Since the switch T was closed when the master controller MC was actuated to the "01T" position, the field windings I4 and |1 of the motors I0 and respectively, are also energized at this time, thereby ensuring that the circulating current builds up rapidly and the dynamic braking action takes effect quickly. The braking current is controlled by means of accelerator resistor 53 in the same manner as during acceleration of 65 the motors, the operation of the pilot motor being under control of the limit relay L which is adjusted by means of the variable load device associated with the truck 60, as hereinbefore described. The pilot motor 44 is operated in a direction to cause the accelerator A to decrease the resistance in the dynamic braking circuit as the speed of the vehicle decreases. The energizing circuit for the pilot motor 44 extends from a contact finger |56 on the braking controller BC which is connected to the conductor |35 and thence to the pilot motor 44 through the circuit previously traced.

Since the shunt 51 is connected in the motor circuit during dynamic braking, the variable load device on, the truck fu'nctions to adjust the setting of the limit relay L in accordance with the load on the vehicle and the relay L governs the motor current to maintain a substantially constant rate of deceleration in the same manner as during the acceleration of the vehicle.

From the foregoing description, it is apparent that I have provided for maintaining substantially constant rates of acceleration and deceleration of an electrically propelled vehicle regardless of changes in the load upon the vehicle within predetermined load limits.

I do not desire to be restricted to the specific embodiment of my invention herein shown and described, since it is evident that it may be changed and modied without departing from the spirit and scope of my invention as defined in the appended claims.

I claim as my invention:

l. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current. means for operating said resistance varying means, a current limit relay responsive to the motor current for controlling the operation of said operating means, and means actuated in accordance with the load on the vehicle for varying the proportionate amount of the motor current passing through said relay.

2. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current, means for operating said resistance varying means, a current limit relay for controlling the operation of said operating means, a variable shunt disposed in the motor circuit for energizing the limit relay proportionally to the motor current, and means actuated in accordance with the load on the vehicle for varying said shunt to change the proportionate amount of the motor current passing through said relay.

3. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, means for operating said resistance varying means, current responsive means for controlling the operation of said operating means, and means actuated in accordance with the load on the vehicle for changing the setting of said current responsive means.

4. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, means for operating said resistance varying means, current responsive means for controlling the operation of said operating means, and means mechanically actuated by variations in the load on the vehicle for varying the motor current required to operate said current responsive means. 5. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, means for operating said resistance varying means in one direction during acceleration of the vehicle, means responsive to the motor current for controlling the operation of said operating means, and means mechanically actuated by variations in the load on the vehicle for varying the proportionate amount of motor current passing through said current responsive means.

6. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistance varying means being utilized to control the motor current during dynamic braking, a pilot motor for operating said resistance varying in one direction during acceleration and in the opposite direction during deceleration of the Vehicle, relay means responsive to the motor current for controlling the operation of the pilot motor, and means mechanically actuated by va riations in the load on the vehicle for changing the setting of the relay means.

'7. In a motor control system, in combination, a motor for propelling a vehicle, resistance varying means for controlling the motor current during acceleration of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistq ance varying means being utilized te control motor current during dynamic bra g, e motor for operating said resismnce'varying one direction during acceleration and in the cp posite direction during deceleration ci? the ve hicle, a current limit relay for controlling the operation of the pilot-motor, a shunt disposed in the motor circuit for energizing the limit relay proportionally to the motor current, and mechanically actuated by variations in the load on the vehicle for varying said shunt change the proportionate amount of the motor current passing through said relay.

8. In a motor control system, in ccrnbinatior l5 a motor for propelling a Vehicle, resistance "if- .t ing means for controlling the motor current ing acceleration of the vehicle, switching means for establishing dynamic braking connections for the motor to decelerate the vehicle, said resistv1 ance varying means being utilized tc control braling motor current during dynamic pilot motor for operating Varying in one direction tion and in the opposite direction ation ofthe vehicle, e. cnil. controlling the operation ci t, variable shunt disposed in the energizing the limit relay proportionally motor current, a movable f 'varying shunt, and means for actuating said a cordance with the load on the vehicle i the energizatlon of said relay. 

